1. Field
The present invention relates to wireless data communication. More particularly, the present invention relates to a novel and improved method and apparatus for code assignment in a spread-spectrum wireless communication system.
2. Background
In a spread spectrum wireless communication system, a base station communicates with multiple mobile users. In one system, a Code Division Multiple Access (CDMA) system, such as specified in the “TIA/EIA/IS-95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,” hereinafter referred to as “the IS-95 standard,” or the “TIA/EIA/IS-2000 Standards for cdma2000 Spread Spectrum Systems,” hereinafter referred to as “the cdma2000 standard,” codes are applied to the data and control information. The codes identify the target recipient as well as the sender. Operation of a CDMA system is described in U.S. Pat. No. 4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” and also in U.S. Pat. No. 5,103,459, entitled “SYSTEM AND METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM,” both assigned to the assignee of the present application for patent and hereby expressly incorporated by reference. The forward link from base station to mobile users assigns a unique Walsh code to each mobile with which it transmits, wherein the Walsh code identifies the mobile. Similarly, the reverse link from the mobile user to the base station uses a Pseudorandom Noise (PN) code for channelization.
Alternate spread spectrum systems incorporate a variety of codes for the two-way identification. A problem exists as codes may be reused in neighboring cells and/or sectors, creating interference for adjacent neighbors. Therefore, a method is needed to provide the two-way identification of wireless communications while minimizing and/or reducing the interference experienced by neighboring cells and/or sectors. Similarly, there is a need for a code assignment method that achieves that reduces neighbor interference.